In one implementation, a transmission apparatus includes a protocol stack for a DSL transmission system, the protocol stack includes a retransmission functionality, the retransmission functionality being provided between a sublayer of a TPS-TC layer and a data link layer, the retransmission functionality having a fragment of a packet or a group of fragments of a packet as basic retransmission unit. The protocol stack may implement a service specific retransmission functionality such that for a first class of services retransmission protection is provided and for a second class of services no retransmission protection is implemented.